The human eye includes a specialized structure referred to as the cornea. The cornea is a multi-layered structure, however, the three most superficial layers—the corneal epithelium, Bowman's Membrane, and the stromal bed—are the layers that are primarily implicated in corneal reformation surgery. The epithelium, which comprises the delicate covering of the human cornea and is only five or six cells thick, is the protective barrier against infection of the cornea. The cornea, being avascular, has unique immune requirements and an infection in this part of the eye is problematic since systemic antibiotics are relatively ineffective. Therefore, preservation of the epithelial integrity is critical in surgery as well as for general eye care.
The epithelium is adherent to the stromal surface along Bowman's Membrane which is a cell-free zone approximately 7 to 12 microns thick and defines the Basement Membrane. Bowman's Membrane is the most anterior structure of the stromal tissue which is the major lamellar structure of the corneal anatomy. In most surgeries of the cornea, efforts are made to prevent the tearing of the epithelium from Bowman's Membrane because such tearing causes pain, slow visual recovery, and predisposes to corneal infiltrates (precursors to infection).
Some corneal reformation techniques, such as LASIK, require the creation of a flap of corneal epithelium which may result in significant destruction of the stromal bed leading to trauma or even permanent damage to the eyes and compromise eyesight. PRK, on the other hand, removes the upper most layer(s) of corneal epithelium without danger to the underlying stromal bed but requires a long recovery period for the patient.
In LASIK, in order to create a useable flap, the flap must be relatively thick. A thick flap, however, requires corneal reformation by ablating underlying tissue that extends into the stromal bed of the cornea. Ablating this tissue has severe consequences. Unless sufficient tissue remains in the stromal bed, the cornea can destabilize resulting in keratoectasia. A patient's long recovery time after PRK surgery is disadvantageous for multiple reasons, such as lengthier vulnerability to infection, discomfort, and inability to return to daily routine quickly.
Accordingly, there is a need for a method of corneal reformation that reduces the risk of trauma and permanent damages to the eye while permitting quick recovery.